A. Field of the Invention
This invention relates to the field of solenoid operated electrohydraulic poppet valve assemblies.
B. Background Art
Normally open and normally closed solenoid operated poppet valve assemblies of the cartridge type are well known for installation in manifold blocks. During manufacture, it has been preferred to drill the manifold block so that, for normally closed cartridge valves, pressure is applied to the valve side port while for normally open cartridge valves, the block provides pressure to the bottom port or under the poppet. Thus, in an installed valve assembly of the normally closed type, pressure applied through the side port has been directed over the poppet to aid in the seating of the poppet in normally closed operation. On the other hand, for previously installed normally open valves, the pressure under the poppet is aided in maintaining the poppet normally open.
However, in the field, it has been desired to field change from normally closed to normally open, or vise versa. However, the pressure ports in the manifold have been opposite to their ideal arrangement. For example, to make a field change from normally closed where pressure from the manifold side port is over the poppet, it has been known to spring bias open a normally open assembly to attempt to change the operation of the valve and avoid the undesired and costly redrilling of the manifold. Such a field solution leaves a lot to be desired since pressure applied over the poppet tends to keep the poppet closed and the spring must have more preload force than orifice area times pressure. If the operating pressure rises above that spring preload on a pressure pulse, the assembly has adversely locked up the poppet. Specifically, the pressure times area exceeded the spring load and the poppet has stayed in the orifice whether or not the coil has been energized.
It has been known in a two-stage valve as shown in U.S. Pat. No. 3,903,919 to provide flow from a bottom and side port to over and under the poppet, respectively.
Accordingly, an object of the present invention is an orifice assembly for a cartridge type, single stage solenoid operated valve assembly which reverses the flow coming from the side port or from the bottom port.